Lance Armstrong arrives at a training session during a rest day of the 2010 Tour de France.

Federal prosecutors say they have dropped its doping case against seven-time Tour de France winner Lance Armstrong. For two years, prosecutors looked into allegations that Armstrong and his United States Postal squad used performance-enhancing drugs.

"In a press release, United States Attorney Andre Birotte Jr. says the case has been closed but didn't disclose the reason for the decision.

"Investigators looked at whether a doping program was created to keep Armstrong and his teammates running at the head of the pack while, at least part of the time, they received government sponsorship from the U.S. Postal Service."

As we've reported, Armstrong has been dogged by allegations of doping for years. He has always denied the allegations, saying that he has never taken performance-enhancing drugs.

Several associates testified before a grand jury in Los Angeles after his ex-teammate Floyd Landis leveled doping allegations against Armstrong.

The AP reports that this investigation was led by federal agent Jeff Novitzky who also investigated baseball stars Barry Bonds and Roger Clemens. Back in December, Bonds was sentenced to 30 days in house arrest for an obstruction of justice conviction that stemmed from his doping case.

The Los Angeles Times reports that U.S. Attorney Andre Birotte Jr. said an announcement about the case's closure was needed, because the investigation had already been made public in press reports.

We'll have more on this story as it develops.

Update at 5:39 p.m. ET. 'Great News':

The AP has obtained a statement from Armstrong's lawyer:

"'This is great news,' Armstrong attorney Mark Fabiani said in a statement. 'Lance is pleased that the United States Attorney made the right decision, and he is more determined than ever to devote his time and energy to Livestrong and to the causes that have defined his career.'"